1. Field of the Invention
The present invention relates to a lighted switch device used in in-car instruments, electric home appliances, front doors or equipments and apparatus expected to be used in darkness.
2. Description of Related Art
One known conventional lighted switch device used in meters of automobiles includes a press button, a lighting part provided on the press button, and a plurality of LEDs disposed on a wiring board, and the device is configured to guide light emitted from the LEDs through the lighting part to an emission surface provided on a top portion of the press button (for reference, see Japanese Patent Laid-Open No.2004-146260, FIG. 3 and paragraphs 0016 to 0022).
Also known is a keyhole illumination device including a light guide disposed at a periphery of a keyhole and a light source provided on a side surface or lower surface of the light guide and used in an ignition key of a vehicle; the device is configured to illuminate the periphery of the keyhole through the light guide by light emitted from the light source (for reference, see Japanese Utility Model Laid-Open No.S62-137972, FIG. 1 and page1).
However, in the lighted switch structure as described in Japanese Patent Laid-Open No.2004-146260, because the distance from the LEDs to the emission surface is relatively short, it is difficult to diffuse the light towards the emission surface, and hence the emission surface tends to be one spot illumination. Conversely, if a light diffusion material is introduced in the lighting part to achieve increased light diffusion efficiency, there is a problem that the amount of light emission is reduced.
Furthermore, in the keyhole illumination device as described in Japanese Utility Model Laid-Open No.S62-137972, the device is structured to indicate the position of the keyhole in darkness, however, there is a problem that the light becomes non-uniform in the light guide, because the light source is attached to a portion of the light guide. Therefore, in this device, the structure makes it difficult for light emitted from the light source to go round to the opposite side of the light source.